Printing method for use with dot printer

ABSTRACT

A printing method to increase the printing speed of a dot printer. Before printing on the basis of the dot data representative of an original dot pattern showing fonts, graphics and the like, the original dot pattern is converted by converting M (M≧3) dots successive in the line direction into N (M&gt;N≧2, M≠2N) dots. Then, printing is performed on the basis of the thus converted dot data. In a modification, conversion is performed by converting each dot into n (n≧2) successive intermediate dots in the line direction and when 2n or more intermediate dots are successive, selecting every m {(2n-1)≧m≧(n+1)}-th intermediate dot. In another modification, pattern conversion is effected by converting each dot into n (n≧2) successive intermediate dots, in a zone where printing is possible at the same dot interval as that of the original dot pattern, selecting only dots out of the intermediate dots that are arranged at the same dot interval as that of the original dot pattern, and in the other zone, selecting every m {(2n-1)≧m≧(n+1)}-th intermediate dot.

This application is a continuation of application Ser. No. 07/985,518filed Dec. 2, 1992, which is a continuation of Ser. No. 07/697,126 filedMay 8, 1991, which is a division of Ser. No. 07/622,991 filed Dec. 6,1990, now U.S. Pat. No. 5,208,762.

BACKGROUND OF THE INVENTION

Hitherto, to attain high-speed printing using a wire dot printer, forexample, a method was known (see, for example, Japanese Patent Laid-OpenNo. 60-73852) which comprised the steps of generating a secondary dotpattern from an original dot pattern showing fonts and the like byremoving every other dot from the original dot pattern, and scanning aprint head on the basis of the secondary dot pattern at a speed 2 timesfaster than usual to attain printing.

According to the method comprising the steps of converting the originaldot pattern into the secondary dot pattern by removing every other dotout of the original dot pattern and performing printing on the basis ofthe secondary dot pattern, although the printing speed is doubled, thethus printed dot pattern is significantly distorted as compared with theoriginal dot pattern, resulting in a poor quality of printing.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a printing methodfor use with a dot printer which can increase the printing speed withlittle deterioration in printing quality.

To accomplish the foregoing object, the present invention provides aprinting method which comprises the steps of receiving the dot datarepresentative of an original dot pattern showing fonts, graphics andthe like; converting the pattern of the original dot pattern byconverting M (M≧3) successive dots in the line direction to N (M>N≧2,M≠2N) dots; and performing printing on the basis of the thus converteddot data. Specifically, printing is performed while scanning a printhead at a speed faster than usual, or printing is performed whilescanning the print head at a speed M/N times faster than usual. In amodification, the foregoing object can also be accomplished by aprinting method which comprises the steps of receiving the dot datarepresentative of an original dot pattern showing fonts, graphics andthe like; converting the pattern of the original dot pattern byconverting each dot to n (n≧2) intermediate successive dots in the linedirection and when 2n or more intermediate dots are successive,selecting every m {(2n-1)≧m≧(n+1)}-th intermediate dot; and performingprinting on the basis of the thus converted dot data. Specifically,printing is performed while scanning a print head at a speed faster thanusual. In another modification, the foregoing object can also beaccomplished by a printing method which comprises the steps of receivingthe dot data representative of an original dot pattern showing fonts,graphics and the like; when printing is to be .performed at a speedfaster than the moving speed of a print head attained when the originaldot pattern is printed, converting the pattern of the original dotpattern by converting each dot into n (n≧2) successive intermediatedots, in a zone where printing is possible at the same dot interval asthat of the original dot pattern, selecting only dots from theintermediate dots that are arranged at the same dot interval as that ofthe original dot pattern, and in the other zone, selecting every m{(2n-1)≧m≧(n+1)}-th intermediate dot; and performing printing on thebasis of the thus converted dot data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a system according to the presentinvention;

FIG. 2 is a flowchart showing a first operation mode of the system shownin FIG. 1;

FIG. 3 is a diagram explanatory of the first operation mode of thesystem shown in FIG. 1;

FIG. 4 is a diagram showing a printed example based on an original dotpattern;

FIG. 5 is a diagram showing a printed example based on the firstembodiment;

FIGS. 6 and 7 are diagrams explanatory of the first operation mode ofthe system shown in FIG. 1;

FIG. 8 is a flowchart showing a second operation mode of the systemshown in FIG. 1;

FIGS. 9 and 10 are diagrams explanatory of the second operation mode ofthe system shown in FIG. 1;

FIG. 11 is a flowcharg showing a third operation mode of the systemshown in FIG. 1;

FIG. 12 is a diagram explanatory of the third operation mode of thesystem shown in FIG. 1;

FIGS. 13 and 14 are diagrams each showing original dot patterns, printedexamples based on the second embodiment, and printed examples based onthe third embodiment, respectively;

FIG. 15 is a diagram showing a printed example based on the thirdembodiment; and

FIG. 16 is a diagram explanatory of the third operation mode of thesystem shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be described withreference to the drawings. In FIG. 1, 1 is a print character designatingmeans such as a personal computer, 2 is an original dot pattern storagecircuit comprised of a font ROM in which the dot data representative ofa plurality of original dot patterns showing letters, numerals, symbolsand the like is stored, 3 is a RAM for temporarily storing both the dotdata representative of an original dot pattern read from the originaldot pattern storage circuit 2 and the dot data representative of asecondary dot pattern obtained by converting the original dot pattern inaccordance with a given algorithm, 4 is a control circuit for readingthe dot data from the original dot pattern storage circuit 2, convertingthe pattern of the original dot pattern, controlling printing, and soon, and 5 is a printing means comprising a print head or the like forperforming printing on the basis of the dot data stored in the RAM 3.

When high-speed printing is to be performed, a mode switch (not shown)is turned to select a high-speed print mode, and then the printcharacter designating means 1 is operated to designate print characters.Upon designation of the print character, the dot data representative ofan original dot pattern corresponding to the designated print characteris read from the original dot pattern storage circuit 2, the originaldot pattern is converted in pattern in accordance with a given algorithmby the control circuit 4, and is stored in the RAM 3. Then, printing isperformed by the printing means 5 on the basis of the dot pattern storedin the RAM 3.

A first embodiment of the process of converting the pattern of theoriginal dot pattern by the control circuit 4 will now be described withreference to the flowchart of FIG. 2.

Assume that the dot data representative of one dot line of the originaldot pattern, corresponding to the designated character and read from theoriginal dot pattern storage circuit 2, is stored in the RAM 3 indeveloped form as shown in FIG. 3(a) so that the 1st, 5th, 9th . . . dotpositions have individual dots d . . . d. With respect to the dot data,first, a check is made to determine whether or not a dot is present atthe first dot position. When a dot is present, it is retained there.Then, a check is made to determine if dots are present at the subsequenttwo dot positions (5th and 9th dot positions). When a dot is present atat least one of the two dot positions, a dot is generated at the middleposition between the two dot positions. In this way, three dots areconverted into two dots. The foregoing processing is repeated withrespect to subsequent dots, so that the original dot pattern of one dotline shown in FIG. 3(a) is converted into the arrangement of FIG. 3(b)whose dot interval is 1.5 times longer (step 1).

When the pattern of all dot lines is converted entirely, the print headis scanned on the basis of the thus converted dot data at a speed 1.5times faster than usual, so that printing elements such as printingwires are driven at the maximum response frequency of the usual printing(step 2).

In this way, letters and the like designated by the print characterdesignating means 1 are printed at a speed 1.5 times faster than usual.

FIG. 4 shows a printed example based on the original dot pattern, andFIG. 5 shows a printed example based on the secondary dot patternobtained by converting the original dot pattern in accordance with thefirst embodiment.

Although the first embodiment converts the pattern starting with theprocess of retaining a dot there, conversion may be performed startingwith the process of generating a dot at the middle position between twosuccessive dot positions as shown in FIG. 6.

Although the first embodiment converts the pattern in such a manner thatthe first process of retaining a dot as it is and the second process ofgenerating a dot at the middle position between two successive dotpositions are alternated, conversion may be performed in such a mannerthat when one or more dot positions have no dot, a then-appearing dot isretained there, and when at least one of subsequent two dot positionshas a dot, a dot is generated at the middle position between them asshown in FIG. 7.

A second embodiment of the, process of converting the original dotpattern by the control circuit 4 will be described with reference to theflowchart of FIG. 8.

Assume that the dot data representative of one dot line of the originaldot pattern is stored in the RAM 3 in developed form as shown in FIG.9(a). With respect to each dot, first, four intermediate dots aregenerated and stored successively (step 1) as shown in FIG. 9(b).

Then, only dots from the intermediate does that are present at dotpositions spaced from the first dot position by an integral multiple ofa dot interval 1.5 times longer than usual are selected, and the otherintermediate dots are removed. As a result, successive dots from the dotdata representative of one dot line shown in FIG. 9(a) are convertedinto those arranged at dot intervals of 1.5 times longer than usual(step 2). as shown in FIG. 9(c).

When the pattern of all dot lines is converted entirely, the print headis scanned on the basis of the thus-converted dot data at a speed 1.5times faster than usual, so that the printing elements such as printingwires are driven at the maximum response frequency of usual printing(step 3).

In this way, letters and the like designated by the print characterdesignating means 1 are printed at a speed 1.5 times faster than usual.

A printed example of the secondary dot pattern obtained by convertingthe original dot pattern shown in FIG. 4 in accordance with the secondembodiment is identical with the printed example of the first embodimentshown in FIG. 5.

Although the second embodiment converts the pattern in such a mannerthat only dots out of the intermediate dots that are arranged at dotintervals of 1.5 times longer than usual are selected, conversion may beperformed in such a manner that when no intermediate dot is present atsome successive dot positions as shown in FIG. 10, a then-appearingintermediate dot is retained there, and only dots from the subsequentintermediate dots that are arranged at dot intervals of 1.5 times longerthan usual are selected.

Although the processes described above with reference to FIGS. 9 and 10select dots arranged at dot intervals of 1.5 times longer than usual,dots arranged at dot intervals of 1.25 or 1.75 times longer than usualmay be selected. For example, in FIG. 9, every 5th intermediate dot maybe selected instead of every 6th intermediate dot; in this case, thescanning speed of the print head is increased to 1.25 times faster thanusual so that printing can be attained at a speed 1.25 times faster thanusual. Similarly, every 7th intermediate dot may be selected instead ofevery 6th intermediate dot; in this case, the scanning speed of theprint head is increased to 1.75 times faster than usual so that printingcan be attained at a speed 1.75 times faster than usual.

Although each of the foregoing embodiments converts one dot into foursuccessive intermediate dots, by giving an adequate storage capacity tothe RAM 3, one dot can be converted into n (n≧2) intermediate dots; inthis case, when there are 2n or moire successive intermediate dots, byselecting every m {(2n-1)≧m≧(n+1)}-th intermediate dot and increasingthe scanning speed of the print head to K (1<K<2) times, preferablyK=m/n, printing can be attained at a speed of K times faster.

A third embodiment of the conversion of the pattern of the original dotpattern by the control circuit will now be described with reference tothe flowchart of FIG. 11.

Generally, the maximum response frequency of the printing elements suchas wire pins is determined by the condition that all dots of one lineare successively printed, and the usual scanning speed of the print headis determined such that the character will be printed optimally when theprinting elements are driven at that maximum response frequency.Practically, however, where only two or three successive dots are to beprinted, the printing elements can be driven at a response frequencyhigher than the maximum response frequency. This embodiment is based onthe assumption that the printing means 5 can print the last one ofsuccessive dots, i.e. two successive dots, at a response frequency 1.5times higher than usual, and intends to improve the printing quality bymaking use of the foregoing property.

Assume that the dot data representative of one dot line of the originaldot pattern is stored in the RAM 3 in developed form as shown in FIG.12(a). First, each dot is converted to two successive intermediate dots(step 1) as shown in FIG. 12(b).

Then, the first intermediate dot is selected, and a check is made todetermine whether or not the number x of successive intermediate dotssubsequent to the thus selected dot meets the condition: n≦x≦2n-1 (n isthe number of intermediate dots generated on the basis of one originaldot; n=2 in this example). When the condition is fulfilled, i.e. whenthere is only one dot which can be successively selected, printing canbe performed at a response frequency of 1.5 times higher than usual;therefore, a dot present at a dot position spaced from the first dotposition by the same dot interval as that of the original dot pattern (adot d1 in FIG. 12(c)) is selected. On the other hand, when x≧2n, i.e.when there are two or more dots which can be successively selected,since the usual response frequency is used for driving, intermediatedots present at dot positions spaced from each other by a dot interval1.5 times longer than usual (a dot d2 in FIG. 12(c)) are selected. Inthis way, all dots except the thus selected dots are removed;consequently, the dot data representative of one dot line shown in FIG.12(a) is converted into the arrangement of FIG. 12(c) (step 2).

When the pattern of all dot lines is converted entirely, the print headis scanned on the basis of the thus converted dot data at a speed 1.5times faster than usual, so that the printing elements such as printingwires are driven at the maximum response frequency of usual printing, orat a response frequency 1.5 times higher than the maximum responsefrequency, to attain print (step 3).

In this way, letters and the like designated by the print characterdesignating means 1 are printed at a speed 1.5 times faster than usual.

For illustrative purposes, FIG. 13(a) shows an original dot pattern, (b)shows a secondary dot pattern obtained by converting the original dotpattern (a) in accordance with the second embodiment, and (c) shows asecondary dot pattern obtained by converting the original dot pattern(a) in accordance with the third embodiment. The secondary dot pattern(b) has bold vertical lines as compared with the original dot pattern(because the dot interval is increased to 1.5 times) and its right upperand lower portions are slightly distorted; but, such points are improvedin the pattern (c), or the pattern (c) is closer to the original dotpattern.

Further, FIG. 14(a) shows an original dot pattern, (b) shows a secondarydot pattern obtained by converting the original dot pattern (a) inaccordance with the second embodiment, and (c) shows a secondary dotpattern obtained by converting the original dot pattern (a) inaccordance with the third embodiment. The secondary dot pattern (b) hasdistorted oblique lines as compared with the original dot pattern; but,such points are improved in the pattern (c), or the pattern (c) hassmooth oblique lines as is the case of the original dot pattern.

FIG. 15 shows a printed example of a secondary dot pattern obtained byconverting the original dot pattern shown in FIG. 4 in accordance withthe third embodiment.

Although the third embodiment converts each dot of the original dotpattern to two intermediate dots, as shown in FIGS. 16(a) and (b), eachdot of the original dot pattern may be converted to four intermediatedots. In this case, as shown in FIG. 16(c), in response to the maximumresponse frequency of the printing elements attained in successive dotprinting of short period, only dots out of successive intermediate dotsthat are present at dot positions spaced from the first dot position byan integral multiple of a dot interval 1.25 or 1.75 times longer thanusual are selected. When the number x of successive intermediate dotssubsequent to the thus selected dot meets the condition: n≦x≦2n-1 (n=4in this example), a dot present at a dot position spaced from that dotposition by the same dot interval as that of the original dot pattern isselected. Consequently, it is possible to attain printing at a speed1.25 or 1.75 times faster than usual by increasing the scanning speed ofthe print head to 1.25 or 1.75 times faster than usual.

Although the third embodiment makes it possible for the printing means 5to print two successive dots at a response frequency higher than theusual maximum response frequency, it is also possible to print three ormore successive dots at a response frequency higher than the usualmaximum response frequency. For this purpose, proper intermediate dotscompatible with such performance will be selected.

Although each of the foregoing embodiments stores the dot datarepresentative of one line in the RAM 3 in developed form, the dot datarepresentative of one character may be stored.

Although each of the foregoing embodiments converts the pattern afterstoring the dot data representative of the original dot pattern in theRAM 3 in developed form, conversion may be performed while the dot datarepresentative of the original dot pattern is being read from theoriginal dot pattern storage circuit 2; in this case, only the dot datarepresentative of the coverted dot pattern may be stored in the RAM 3 indeveloped form,

According to the present invention, the printing speed can be increasedwith little deterioration in printing quality, The invention makes itpossible to print the original dot pattern in the form of a dot patterncloser thereto with little degradation of the printing quality.

What we claim is:
 1. A method for printing wherein a printhead issuccessively scanned in a line direction to print a plurality of dotsextending in said line direction and a recording medium is fed at rightangles to said line direction, comprising the steps of:receivingoriginal dot data representative of a given line, in said linedirection, of an original dot pattern including fonts, graphics and thelike, having individual original dots separated from a precedingindividual original dot by a minimum interval d₁ ; converting saidoriginal dots, of said dot data in said given line, into n(n≧2)successive dots of secondary dot data, wherein n is an integer and eachsuccessive dot is separated by a secondary interval being equal to d₁/n; selecting desired dots of said secondary dot data in the linedirection, wherein said desired dots having an interval d₁ or d₂ betweensaid desired dots, wherein d₂ =d₁ ×m/n and m>n; scanning the printheadat a sped faster than a speed attained when the original dot pattern isprinted; printing in the line direction using the thus selected desireddots driving a printing element of the printhead at a shorter cycle ratethan used to print said original dot data in response to a predeterminednumber of successive ones of said desired dots; and driving the printingelement at a cycle rate equal to that used to print said original dotdata in response to remaining successive ones of said desired dots.
 2. Amethod for printing wherein a printhead is successively scanned in aline direction to print a plurality of lines extending in said linedirection and a recording medium is fed at right angles to said linedirection, comprising the steps of:receiving dot data representative ofdots of a given line of said plurality of lines extending in said linedirection of an original dot pattern having fonts, graphics and thelike, wherein individual original dots are separated from a precedingindividual original dot in said line direction by a minimum interval;converting the pattern of said original dot pattern in the linedirection by converting said dots of said dot data into n dots ofconverted dot data in the line direction, wherein n is an integer;arranging said dots of said converted dot data successively from a firstdot data position with an interval 1/n times the original dot datainterval and selecting desired dots of said converted dot data, at leasta portion of which are separated by an interval greater than saidminimum interval, while retaining a relative pattern densitysubstantially the same as that of said original dot pattern; scanningthe printhead at a speed faster than the moving speed attained when theoriginal dot pattern is printed; and printing using the thus selecteddot data in the line direction, the driving cycle of a printing element,in response to a predetermined number of successive dots of saidselected dot data, being shorter than the driving cycle of a printingelement when printing an original dot pattern, and the driving cycle ofa printing element, in response to remaining successive dot data of saidselected dot data, being the same as the driving cycle of a printingelement when printing the original dot pattern.
 3. A printing method foruse with a dot printer comprising the steps of:receiving scanned linesof original dot data representative of an original dot pattern; printingat a scan speed faster than the moving speed of a printhead along a scandirection attained when the original dot pattern is printed by patternconverting the original dot pattern; said pattern convertingincluding:converting each dot of the original dot pattern, in anindividual one of said plurality of scanned lines, into n(n≧2)successive intermediate dots along said scan direction; selecting onlydots out of the intermediate dots that are arranged at the same dotinterval in said scan direction as that of the original dot pattern overa zone where printing at original dot density is possible at the fasterscan speed, and in another zone, selecting every m_(th) intermediate dot(2n-1≧m≧n+1), thereby reducing a density of said dots in said scandirection to permit said faster scan speed.
 4. A method for printingcharacters, graphics or the like by means of a dot printer having aprinthead movable for scanning in a line direction relative to arecording medium, said method comprising the steps of:receiving originaldot data which represents an original dot pattern having dots providedin said line direction while keeping a distance d₁ between said dots insaid line direction; converting the original dot pattern by convertingeach original dot data into n(n≧2) successive secondary dot data in saidline direction, wherein n is an integer and each successive dot isseparated by a secondary interval being equal to d₁ /n; selectingdesired secondary dot data of which a dot data interval is equal to orbroader than the minimum interval of the original dot data in said linedirection; scanning the printhead at a speed V₂, which is faster than ascanning speed V₁, which is a scanning speed when printing is performedby the original dot pattern and printing the thus selected secondary dotdata; and the distance between the printed dots, in said line directionusing the selected secondary dot data, being equal to or broader thanthe distance d₁.
 5. A method according to claim 4 wherein the distancebetween the printed dots using the selected secondary dot data is equalto d₁ or d₂, wherein d₂ =d₁.V₂ /V₁.
 6. A method for increasing aprinting speed of a dot printer of the type in which a printhead issuccessively scanned across a recording medium in a scan line directionto produce a plurality of scan lines of dot data, said recording mediumis fed incrementally at right angles to said scan line direction uponcompletion of a successive scanning across said recording medium by saidprinthead, and each of said plurality of scan lines of dot data is madeup of a row of individual dots formed by driving at least one printingelement disposed in said printhead as said printhead is scanned acrosssaid recording medium, comprising the steps of:receiving a scan line oforiginal dot data including a plurality of individual original dots,wherein each of said individual original dots is separated from apreceding individual original dot in said row by a minimum interval d₁ ;converting said scan line of original dot data into intermediate dotdata by converting each of said individual original dots intointermediate dot segments each comprised of n successive intermediatedots wherein a first intermediate dot in each of said intermediate dotsegments occupies a position of each of said individual original dots,and each successive intermediate dot in each of said intermediate dotsegments is separated from a preceding intermediate dot by anintermediate interval equal to d₁ /n, wherein n≧2 and n is an integer;consecutive ones of said intermediate dots forming a group including atleast one of said intermediate dot segments; converting saidintermediate dot data into secondary dot data including secondary dotsseparated by at least one of intervals d₂ and d₃, wherein d₂ ≧d₁, d₃>d₁, and d₃ >d₂ ; and scanning said printhead to print said secondarydata at a secondary speed V₂, said secondary speed being greater than anoriginal scanning speed V₁ when printing is performed by said originaldot data.
 7. The method according to claim 6, wherein said step ofconverting further includes:selecting an individual one of saidsuccessive intermediate dots occupying a first position in said group;determining a number x of remaining successive intermediate dotssubsequent to a most recently selected one of said successiveintermediate dots in each said group; selecting intermediate dote insaid group occupying positions equivalent to said original dot databeing offset from said most recently selected one of said successiveintermediate dots by d₂, when n≧x≧2n-1; selecting intermediate dots insaid group occupying positions offset from said most recently selectedone of said successive intermediate dots by d₃, when x≧2n; and whereinsaid secondary dot data includes intermediate dots selected in saidsteps of selecting.
 8. The method according to claim 6, wherein V₂ /V₁=d₃ /d₁.